Effect of Cation on Physical Properties and CO2 Solubility for Phosphonium-Based Ionic Liquids with 2-Cyanopyrrolide Anions

Transport and Energetics of Carbon Dioxide in Ionic Liquids at Aqueous Interfaces

A major hurdle in utilizing carbon dioxide (CO2) lies in separating it from industrial flue gas mixtures and finding suitable storage methods that enable its application in various industries. To address this issue, we utilized a combination of molecular dynamics simulations and experiments to investigate the behavior of CO2 in common room-temperature ionic liquids (RTIL) when in contact with aqueous interfaces. Our investigation of RTILs, [EMIM][TFSI] and [OMIM][TFSI], and their interaction with a pure water layer mimics the environment of a previously developed ultrathin enzymatic liquid membrane for CO2 separation. We analyzed diffusion constants and viscosity, which reveals that CO2 molecules exhibit faster mobility within the selected ILs compared to what would be predicted solely based on the viscosity of the liquids using the standard Einstein-Stokes relation. Moreover, we calculated the free energy of translocation for various species across the aqueous-IL interface, including CO2 and HCO3-. Free energy profiles demonstrate that CO2 exhibits a more favorable partitioning behavior in the RTILs compared to that in pure water, while a significant barrier hinders the movement of HCO3- from the aqueous layer. Experimental measurement of the CO2 transport in the RTILs corroborates the model. These findings strongly suggest that hydrophobic RTILs could serve as a promising option for selectively transporting CO2 from aqueous media and concentrating it as a preliminary step toward storage.

Ammonium-, phosphonium- and sulfonium-based 2-cyanopyrrolidine ionic liquids for carbon dioxide fixation

The development of carbon dioxide (CO₂) scavengers is an acute problem nowadays because of the global warming problem. Many groups around the globe intensively develop new greenhouse gas scavengers. Room-temperature ionic liquids (RTILs) are seen as a proper starting point to synthesize more environmentally friendly and high-performance sorbents. Aprotic heterocyclic anions (AHA) represent excellent agents for carbon capture and storage technologies. In the present work, we investigate RTILs in which both the weakly coordinating cation and AHA bind CO₂. The ammonium-, phosphonium-, and sulfonium-based 2-cyanopyrrolidines were investigated using the state-of-the-art method to describe the thermochemistry of the CO₂ fixation reactions. The infrared spectra and electronic and structural properties were simulated at the hybrid density functional level of theory to characterize the reactants and products of the chemisorption reactions. We conclude that the proposed CO₂ capturing mechanism is thermodynamically allowed and discuss the difference between different families of RTILs. Quite unusually, the intramolecular electrostatic attraction plays an essential role in stabilizing the zwitterionic products of the CO₂ chemisorption. The difference in chemisorption performance between the families of RTILs is linked to sterical hindrances and nucleophilicities of the α- and β-carbon atoms of the aprotic cations. Our results rationalize previous experimental CO₂ sorption measurements (Brennecke et al., 2021).

Quantification of Ylide Formation in Phosphonium-Based Ionic Liquids Reacted with CO2

Phosphonium-based ionic liquids (ILs) paired with aprotic heterocyclic anions (AHAs) are found to react with CO₂ to form both a carbamate product and a carboxyl product. The carboxyl product is formed primarily at elevated temperatures through the formation of a phosphonium ylide intermediate. The formation of the carboxyl product leads to the formation of the neutral azole, which can lead to an irreversible process if the neutral azole is sufficiently volatile. To understand how the ILs would behave in a CO₂ capture process operated at elevated temperatures, it was necessary to quantify the two reaction products. CO₂ was reacted with seven different AHA ILs to determine the equilibrium amounts of carbamate and carboxyl, the equilibrium constants for both reactions, and the rate of CO₂ absorption by each reaction path. The reactions were tracked and quantified in situ by using ATR-FTIR spectroscopy, while NMR spectroscopy was used after equilibrium was reached to determine the extent of each reaction at multiple temperatures and pressures. It was found that both the basicity and molecular size of the anion play key roles in the formation of the phosphonium ylide. In the extreme case of [P₆₆₆₁₄][4-Triaz] only half of the reacted product was the desired carbamate at 60 °C. Although there is a significant amount of the carboxyl product formed, the carbamate is kinetically favored.

Cation-Anion and Anion-CO2 Interactions in Triethyl(octyl)phosphonium Ionic Liquids with Aprotic Heterocyclic Anions (AHAs)

Ionic liquids with aprotic heterocyclic anions (AHAs) have been developed for postcombustion CO₂ capture applications. The anions of AHA ILs play a significant role in tuning anion-CO₂ complexation. In addition, AHAs are able to trigger the abstraction of acidic protons located at the α position of phosphonium cations by forming hydrogen bonds between cations and anions, eventually leading to cation-driven CO₂ complexation. Here we investigate the role of the anion in cation-anion hydrogen bonding and ylide formation. Using CO₂ uptake measurements, ³¹P nuclear magnetic resonance (NMR), attenuated total reflection-Fourier transform infrared (ATR-FTIR) deuterium exchange equilibrium and rates, two-dimensional nuclear Overhauser effect spectroscopy (2D NOESY), and density functional theory calculations, we show that the key is the proximity of the negatively charged nitrogen atoms on the anion to the α protons, which is governed not just by anion basicity but by sterics. Thus, we show that triethyl(octyl)phosphonium 3-methyl-5-trifluoromethylpyrazolide is much more effective in hydrogen-bonding with and deprotonating the cation than the equivalent [P₂₂₂₈] ILs with more basic 2-cyanopyrrolide and 3-trifluoromethylpyrazolide anions.

The Nature of Carbon Dioxide in Bare Ionic Liquids

Ionic liquids (ILs) are among the most studied and promising materials for selective CO₂ capture and transformation. The high CO₂ sorption capacity associated with the possibility to activate this rather stable molecule through stabilization of ionic/radical species or covalent interactions either with the cation or anion has opened new avenues for CO₂ functionalization. However, recent reports have demonstrated that another simpler and plausible pathway is also involved in the sorption/activation of CO₂ by ILs associated with basic anions. Bare ILs or IL solutions contain almost invariable significant amounts of water and through interaction with CO₂ generate carbonates/bicarbonates rather than carbamic acids or amidates. In these cases, the IL acts as a base and not a nucleophile and yields buffer-like solutions that can be used to shift the equilibrium toward acid products in different CO₂ reutilization reactions. In this Minireview, the emergence of IL buffer-like solutions as a new reactivity paradigm in CO₂ capture and activation is described and analyzed critically, mainly through the evaluation of NMR data.

Potential of Mean Force Calculations for an SN2 Fluorination Reaction in Five Different Imidazolium Ionic Liquid Solvents Using Quantum Mechanics/Molecular Mechanics Molecular Dynamics Simulations

The use of ionic liquids (ILs) as both catalysts and solvents in a wide range of chemical reactions has received considerable attention over the last few years due to their positive effects in enhancing reaction rates and selectivities. In this work, hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations were carried out in conjunction with umbrella-sampling techniques to study the bimolecular nucleophilic substitution (S_N2) fluorination reaction between propyl-mesylate and potassium fluoride using five ILs as solvents, specifically, 1-butyl-3-methylimidazolium mesylate ([C₄mim][OMs]), 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]), 1-butyl-3-methylimidazolium trifluoroacetate ([C₄mim][CF₃COO]), 1-butyl-3-methylimidazolium bromide ([C₄mim][Br]), and 1-butyl-3-methylimidazolium chloride ([C₄mim][Cl]) at 373.15 K. The QM region (reactive part) in all QM/MM systems was simulated using the Parametric Method 6 (PM6) semiempirical methods, and for the MM region (IL solvent), classical force fields (FF) were employed, with the FF developed within the group. The calculated activation free energy barriers (ΔG^‡) for the S_N2 reaction in the presence of [C₄mim][OMs] and [C₄mim][BF₄] ILs were in agreement with the experimental values reported in the literature. On the other hand, only predicted values were obtained for the activation energies for the [C₄mim][CF₃COO], [C₄mim][Br], and [C₄mim][Cl] ILs. These activation energies indicated that the S_N2 reaction would be more facile to proceed using the [C₄mim][Cl] and [C₄mim][OMs] ILs, in contrast with the use of [C₄mim][Br] IL, which presented the highest activation energy. Energy-pair distributions, radial distribution functions, and noncovalent interactions (NCI) were also calculated to elucidate the molecular interactions between the reactive QM region and the solvents or reaction media. From these calculations, it was found that not only the reactivity can be enhanced by selecting a specific anion to increase the K-F separation but also the cation plays a relevant role, producing a synergetic effect by forming hydrogen bonds with the fluorine atom from KF and with the oxygen atoms within the mesylate leaving group. Three interactions are significant for the IL catalytic behavior, F_QM-HX, K_QM-anion, and O_QM-HX interactions, where the F_QM and K_QM labels correspond to fluorine and potassium atoms from the KF salt, O_QM corresponds to oxygen atoms within the mesylate leaving group (reactant), and HX refers to hydrogen atoms within the IL cation. The NCI analysis revealed that K_QM-anion interactions are of weak type, indicating the importance of hydrogen bond interactions from the cation such as F_QM-HX and O_QM-HX for the catalytic behavior of ILs.

Cooperative CO2 absorption by amino acid-based ionic liquids with balanced dual sites

In this study, a variety of functionalized ILs with dual sites including amino acid group (AA) and basic anion (R) were synthesized to investigate the suppression and cooperation between the sites in CO₂ absorption. The basic anions selected in this study with different basicity include sulfonate (Su), carboxylate (Ac), imidazolium (Im), and indolium (Ind). These ILs ([P₆₆₆₁₄]₂[AA-R]) were applied to CO₂ absorption. The results present that CO₂ capacity increases first and then decreases later with the continuous increase in the activity of the anion site. Combined with CO₂ absorption experiments, IR and NMR spectroscopic analyses and DFT calculation demonstrate that the ability of one site to capture CO₂ would be suppressed when the activity of another site is much stronger. Thus, the cooperation of dual site-functionalized ILs and high CO₂ capacity might be achieved through balancing the two sites to be equivalent. Based on this point, [P₆₆₆₁₄]₂[5Am-iPA] was further synthesized by taking the advantage of the conjugated benzene ring. As expected, [P₆₆₆₁₄]₂[5Am-iPA] showed capacity as high as 2.38 mol CO₂ per mol IL at 30 °C and 1 bar without capacity decrease even after 10 times recycling performance of CO₂ absorption and desorption.

Reaction Mechanism and Free Energy Barriers for the Chemisorption of CO2 by Ionic Entities

Ionic liquids, a class of alternative solvents, are known for their ability to capture carbon dioxide (CO₂). The understanding of the role of the individual ionic entity of the ionic liquid (IL) and the involved mechanism is essential to design a better solvent for the capture process. In the present study, we employed density functional theory based electronic structure calculations and metadynamics method based first-principles molecular dynamics (FPMD) simulations to investigate the roles of the cation and anion of the IL by analyzing the energetics and free energy profile of the involved chemical reactions. The mechanism of chemisorption of CO₂ by the aprotic N-heterocyclic and phenolate anions paired with tetrapropyl phosphonium cation [P₃₃₃₃] were studied to understand the reaction mechanism of the initial capture process. The process of uptaking of CO₂ by the [P₃₃₃₃][1,2,4-Triz] was studied by the first-principles calculations. The transition states in the reaction pathways were computed by the synchronous transit-guided quasi-Newton method and confirmed by the intrinsic reaction coordinate calculations using first-principles simulations. The dynamics of the energetics of the chemisorption process were studied by constructing the free energy surface using metadynamics-based FPMD simulations. First, the nucleophilic center was generated at the α-carbon of the cation by transferring a proton to the anion with the formation of the phosphorus ylide. The formed cation ylide chemisorbs CO₂ through the formation of a bond between the α-carbon of ylide and the carbon of CO₂. The direct addition of CO₂ to the anion of the ionic pair was studied as the second pathway. We find that the chemisorption of CO₂ by the anion is more favorable than that by the cation. By comparing the chemisorption of CO₂ by the ions, we observe that the deprotonation of the alkyl chain is the more deciding factor, which depends on the basicity of anion and the length of the alkyl chain. We computed the free energy landscapes for the ionic pairs by varying another four anions like cyclohexanolate, 2,4,6-trifluorophenolate, imidazolate, and benzotriazolide paired with tetrapropyl phosphonium cation. The effect of the alkyl chain on the proton transfer was studied by tetrabutyl and tetrapentyl phosphonium cations paired with 1,2,4-triazolide anion. The carbonated product, formed from the anion, is thermodynamically controlled, while the carboxylated product (formed from cation) is kinetically controlled. We hope that our findings will enhance the knowledge of the selectivity of ionic entities for designing IL-based solvents for the capture process of CO₂.

Gas-Phase and Ionic Liquid Experimental and Computational Studies of Imidazole Acidity and Carbon Dioxide Capture

The capture and storage of carbon dioxide are pressing environmental concerns. Nucleophilic capture by anions in ionic liquids, such as imidazolates, is a promising strategy. Herein, the gas-phase acidity of a series of imidazoles is examined both experimentally and computationally. The intrinsic acidity of these imidazoles has not heretofore been measured; these experimental data provide a benchmark for the computational values. The relationship between imidazole acidity and carbon dioxide capture is explored computationally, both in the gas phase and in ionic liquid. The improved understanding of imidazolate properties provided herein is important for the design and development of improved systems for carbon dioxide capture.

Thermally induced characterization and modeling of physicochemical, acoustic, rheological, and thermodynamic properties of novel blends of (HEF + AEP) and (HEF + AMP) for CO2/H2S absorption

CO₂ and H₂S removal from flue gases is indispensable to be done for protection of environment with respect to global warming as well as clean air. Chemical absorption is one of the most developed and capable techniques for the removal of these sour gases. Among the many solvents, ionic liquids (ILs) are more capable due to their desirable green solvent properties. However, ILs being usually costlier, the blends of ILs and amines are more suggestive for absorption. In the present work, various essential characterization properties such as density, viscosity, sound velocity, and refractive index of two ionic liquid-amine blend systems viz. (1) 2-Hydroxy ethyl ammonium formate (HEF) + 1-(2-aminoethyl) piperazine (AEP) and (2) 2-Hydroxy ethyl ammonium formate (HEF) + 2-Amino-2-methyl-1-propanol (AMP) are reported. The temperature range for which all the measurements were conducted is 298.15 to 333.15 K. For both systems of (HEF + AEP) and (HEF + AMP), HEF mass fractions were varied from 0.2 to 0.8.The density and viscosity results were correlated as a function of temperature and concentration of ionic liquid and amine with Redlich-Kister and Grunberg-Nissan models, respectively. Moreover, feed forward neural network model (ANN) is explored for correlating experimentally determined sound velocity and refractive index data. The measured properties are further analyzed to estimate various thermodynamic as well as transport properties such as diffusivity of CO₂/H₂S in the (HEF + AEP) and (HEF + AMP), thermal expansion coefficients, and isentropic compressibility, ΔG⁰, ΔS⁰, ΔH⁰, using the available models in the literature.

Evaluating the Performance of Micro-Encapsulated CO2 Sorbents during CO2 Absorption and Regeneration Cycling

We encapsulated six solvents with novel physical and chemical properties for CO₂ sorption within gas-permeable polymer shells, creating Micro-Encapsulated CO₂ Sorbents (MECS), to improve the CO₂ absorption kinetics and handling of the solvents for postcombustion CO₂ capture from flue gas. The solvents were sodium carbonate (Na₂CO₃) solution, uncatalyzed and with two different promoters, two ionic liquid (IL) solvents, and one CO₂-binding organic liquid (CO₂BOL). We subjected each of the six MECS to multiple CO₂ absorption and regeneration cycles and measured the working CO₂ absorption capacity as a function of time to identify promising candidate MECS for large-scale carbon capture. We discovered that the uncatalyzed Na₂CO₃ and Na₂CO₃-sarcosine MECS had lower CO₂ absorption rates relative to Na₂CO₃-cyclen MECS over 30 min of absorption, while the CO₂BOL Koechanol appeared to permeate through the capsule shell and is thus unsuitable. We rigorously tested the most promising three MECS (Na₂CO₃-cyclen, IL NDIL0309, and IL NDIL0230) by subjecting each of them to a series of 10 absorption/stripping cycles. The CO₂ absorption curves were highly reproducible for these three MECS across 10 cycles, demonstrating successful absorption/regeneration without degradation. As the CO₂ absorption rate is dynamic in time and the CO₂ loading per mass varies among the three most promising MECS, the process design parameters will ultimately dictate the selection of MECS solvent.

Enhanced CO2 capture by reducing cation-anion interactions in hydroxyl-pyridine anion-based ionic liquids

In this work, an efficient strategy for improving CO2 capture based on anion-functionalized ionic liquids (ILs) by reducing cation-anion interactions in ILs was reported. The influence of the cationic species on CO2 absorption was investigated using 2-hydroxyl pyridium anions ([2-Op]) as a probe. CO2 capture experiments indicated that the CO2 absorption capacity in [2-Op] anion-based ILs varied from 0.94 to 1.69 mol CO2 per mol IL at 30 °C and 1 atm. Spectroscopic analysis and quantum chemical calculations suggested that the increase of the CO2 absorption capacity may be ascribed to the reduction of the strength of cation-anion interactions in ILs, and stronger cation-anion interactions would make one CO2 site in the [2-Op] anion inactive. Furthermore, the effect of the cation unit on the anion was evidenced by FT-IR spectra, implying that strong interactions between ions may lead to the decrease of the IR absorption wavenumber of hydroxy pyridium and work against CO2 capture. Following this strategy, it was finally found that [Ph-C8eim][2-Op] (Ph-C8eim = 1-N-ethyl-3-N-octyl-2-phenylimidazolium) with weaker cation-anion interactions exhibited a significant increase in the CO2 uptake capacity, and extremely high capacities of 1.69 and 1.83 mol CO2 per mol IL could be achieved at 30 and 20 °C, respectively. The study presented here would be helpful for further designing novel and effective ILs for advancing CO2 capturing performance.

Reaction Ensemble Monte Carlo Simulations of CO2 Absorption in the Reactive Ionic Liquid Triethyl(octyl)phosphonium 2-Cyanopyrrolide

The absorption of CO₂ into an aprotic heterocyclic anion ionic liquid (IL) is modeled using reaction ensemble Monte Carlo (RxMC) with the semigrand reaction move. RxMC has previously been unable to sample chemical equilibrium involving molecular ions in nanostructured liquids due to the high free-energy requirements to open and close cavities and restructure the surrounding environment. Our results are validated by experiments in the modeled IL, triethyl(octyl)phosphonium 2-cyanopyrrolide ([P₂₂₂₈][cnp]), and in a close analog with longer alkyl chains on the cation. Heats of absorption and reaction from both experiment and simulation are exothermic and of comparable magnitude. Replacing experimental Henry's constants with their simulated counterparts improves the accuracy of a Langmuir-type model at moderate pressures. Nonidealities that affect chemical equilibrium are identified and calculated with high precision.

Encapsulation of Ionic Liquids with an Aprotic Heterocyclic Anion (AHA-IL) for CO2 Capture: Preserving the Favorable Thermodynamics and Enhancing the Kinetics of Absorption

The performance of an ionic liquid with an aprotic heterocyclic anion (AHA-IL), trihexyl(tetradecyl)phosphonium 2-cyanopyrrolide ([P₆₆₆₁₄][2-CNPyr]), for CO₂ capture has been evaluated considering both the thermodynamics and the kinetics of the phenomena. Absorption gravimetric measurements of the gas-liquid equilibrium isotherms of CO₂-AHA-IL systems were carried out from 298 to 333 K and at pressures up to 15 bar, analyzing the role of both chemical and physical absorption phenomena in the overall CO₂ solubility in the AHA-IL, as has been done previously. In addition, the kinetics of the CO₂ chemical absorption process was evaluated by in situ Fourier transform infrared spectroscopy-attenuated total reflection, following the characteristic vibrational signals of the reactants and products over the reaction time. A chemical absorption model was used to describe the time-dependent concentration of species involved in the reactive absorption, obtaining kinetic parameters (such as chemical reaction kinetic constants and diffusion coefficients) as a function of temperatures and pressures. As expected, the results demonstrate that the CO₂ absorption rate is mass-transfer-controlled because of the relatively high viscosity of AHA-IL. The AHA-IL was encapsulated in a porous carbon sphere (Encapsulated Ionic Liquid, ENIL) to improve the kinetic performance of the AHA-IL for CO₂ capture. The newly synthesized AHA-ENIL material was evaluated as a CO₂ sorbent with gravimetric absorption measurements. AHA-ENIL systems preserve the good CO₂ absorption capacity of the AHA-IL but drastically enhance the CO₂ absorption rate because of the increased gas-liquid surface contact area achieved by solvent encapsulation.

Investigation of furoate-based ionic liquid as efficient SO2 absorbent

A series of furoate-based ionic liquids with good absorption and separation performance for SO₂ were reported.

Molecular dynamics and a spectroscopic study of sulfur dioxide absorption by an ionic liquid and its mixtures with PEO

An investigation comprising experimental techniques (absorption capacity of SO₂ and vibrational spectroscopy) and molecular simulations (thermodynamics, structure, and dynamics) has been performed for the polymer poly(ethylene oxide) (PEO), the ionic liquid butyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([N₄₁₁₁][Tf₂N]) and their mixtures as sulfur dioxide (SO₂) absorbing materials. The polymer PEO has higher capacity to absorb SO₂ than the neat ionic liquid, whereas the mixtures presented intermediary absorption capacities. The band assigned to the symmetric stretching band of SO₂ at ca. 1140 cm^-1, which is considered a spectroscopic probe for the strength of SO₂ interactions with its neighborhood, shifts to lower wavenumbers as more negative total interaction energy values of SO₂ were evaluated from the simulations. The solvation free energy of SO₂, ΔG_sol, correlates linearly with the absorption capacity of SO₂. The negative values of ΔG_sol are due to negative and positive values of enthalpy and entropy, respectively. In the ionic liquid, SO₂ weakens the cation-anion interactions, whereas in the mixture with a high content of PEO these interactions are slightly increased. Such effects were correlated with the relative population of cisoid and transoid conformers of Tf₂N anions as revealed by Raman spectroscopy. Moreover, the presence of SO₂ in the systems provokes the increase of diffusion coefficients of the absorbing species in comparison with the systems without the gas. Proper to the slow dynamics of the polymer, the diffusion coefficient of ions and SO₂ diminishes with the increase of the PEO content.

Encapsulated Ionic Liquids for CO2 Capture: Using 1-Butyl-methylimidazolium Acetate for Quick and Reversible CO2 Chemical Absorption

The potential advantages of applying encapsulated ionic liquid (ENIL) to CO₂ capture by chemical absorption with 1-butyl-3-methylimidazolium acetate [bmim][acetate] are evaluated. The [bmim][acetate]-ENIL is a particle material with solid appearance and 70 % w/w in ionic liquid (IL). The performance of this material as CO₂ sorbent was evaluated by gravimetric and fixed-bed sorption experiments at different temperatures and CO₂ partial pressures. ENIL maintains the favourable thermodynamic properties of the neat IL regarding CO₂ absorption. Remarkably, a drastic increase of CO₂ sorption rates was achieved using ENIL, related to much higher contact area after discretization. In addition, experiments demonstrate reversibility of the chemical reaction and the efficient ENIL regeneration, mainly hindered by the unfavourable transport properties. The common drawback of ILs as CO₂ chemical absorbents (low absorption rate and difficulties in solvent regeneration) are overcome by using ENIL systems.

Understanding the hydrogen bonds in ionic liquids and their roles in properties and reactions

Ionic liquids (ILs) have many potential applications in the chemical industry. In order to understand ILs, their molecular details have been extensively investigated. Intuitively, electrostatic forces are solely important in ILs. However, experiments and calculations have provided strong evidence for the existence of H-bonds in ILs and their roles in the properties and applications of ILs. As a structure-directing force, H-bonds are responsible for ionic pairing, stacking and self-assembling. Their geometric structure, interaction energy and electronic configuration in the ion-pairs of imidazolium-based ILs and protic ionic liquids (PILs) show a great number of differences compared to conventional H-bonds. In particular, their cooperation with electrostatic, dispersion and π interactions embodies the physical nature of H-bonds in ILs, which anomalously influences their properties, leading to a decrease in their melting points and viscosities and thus fluidizing them. Using ILs as catalysts and solvents, many reactions can be activated by the presence of H-bonds, which reduce the reaction barriers and stabilize the transition states. In the dissolution of lignocellulosic biomass by ILs, H-bonds exhibit a most important role in disrupting the H-bonding network of cellulose and controlling microscopic ordering into domains. In this article, a critical review is presented regarding the structural features of H-bonds in ILs and PILs, the correlation between H-bonds and the properties of ILs, and the roles of H-bonds in typical reactions.

Active chemisorption sites in functionalized ionic liquids for carbon capture

Carbon capture with site-containing ionic liquids is reviewed with particular attention on the activation and design of the interaction sites.